Ruminant animals, including cattle, sheep, giraffe, deer, goats, bison and camels, and more particularly the domesticated species comprise an important group of animals that require periodic administration of medicines, nutrients and other biologically active agents (which are hereinafter referred to in their broadest sense as "drugs") for the treatment and alleviation of various conditions and for better health.
Ruminants have a complex three or four compartment stomach, with the rumen being the largest compartment. The rumen, including the reticulum (hereafter referred to as the "rumen") serves as an important organ for locating dispensing device for delivering medicines and nutrients to such animals over extended periods of time.
There are numerous ruminal delivery devices known in the art which are capable of prolongedly releasing drugs. Typically, these devices are swallowed by the ruminant or otherwise mechanically introduced into the rumen by means of a bolus gun for example, and remain therein for a long period of time without being regurgitated or otherwise eliminated. Typical devices are those disclosed in U.S. Pat. Nos. 4,505,711, 4,578,263, 4,595,553, 4,612,186, 4,623,345, 4,642,230, 4,643,393 and 4,675,179 incorporated herein by reference.
In order to insure that these devices remain in the rumen for a prolonged period of time a density element is often incorporated into the device. Typically, the density element is manufactured from a material such as iron or steel, iron oxide, magnesium, zinc, cobalt oxide, copper oxide or mixtures thereof, metal shot or parts which may be coated with iron oxide, zinc, magnesium alloy, copper oxide, mixtures of cobalt oxide and iron powder and unsintered, compacted metal powders, and the like. Such density elements typically have sufficient density to bring the overall density of the delivery device to a level greater than the density of ruminal fluid (approximately 1 gm/cm.sup.3) and typically to an overall density of at least 2 gm/cm.sup.3.
In animals such as cattle raised for slaughter the density element will remain in the carcass after slaughter. The rumen and ruminal contents of animals still containing ruminal delivery devices, including their density elements, are typically processed by rendering plants. Rendering plants comprise a highly automated and continuous operation and though such machinery is typically equipped with magnetic retrieval systems, these systems are not always effective for removing the density elements. As a result, the density elements have caused extensive and costly damage to grinder blades, guillotines, rollers and other equipment.
In addition, it has been found that density elements made from materials such as iron, magnesium or zinc which corrode in water or ruminal fluid and generate gases which interfere with the proper operation of fluid activated delivery devices such as those shown in U.S. Pat. Nos. 4,595,553, 4,612,186 and 4,675,174, for example.